Is this homebrew Dragon Rider class balanced compared to the other classes in 5e?

Dragons terrify most adventures, but for you, one very small dragon decided to bond with you, giving you the gift of magic as well. Why did the dragon choose you? Did your country or city test every citizen for a bond? Did you find your dragon still in an egg while exploring a abandoned dragon cave far greater adventurers cleared years before? Did you stumble upon it in the woods one day while hunting? Are the dragon’s parents or a military looking for it?

Quick Build:
Intelligence should be your highest score as a Rider, followed by Constitution or Strength/Dexterity. Get starting equipment c and choose the spells Faerie Fire, Hunter’s Mark, Arcane Weapon, and Thunderous Smite.

Dragon Rider Spell List
Arcane Weapon
Ensnaring Strike
Expeditious Retreat
Faerie Fire
Fog Cloud
Hail of Thorns
Hunter’s Mark
Searing Smite
Thunderous Smite
Wrathful Smite
Zephyr Strike
Alter Self
Branding Smite
Magic Weapon
Warding Wind
Blinding Smite
Call Lightning
Crusader’s Mantle
Elemental Weapon
Flame Arrows
Lightning Arrow
Protection from Energy
Vampiric Touch
Elemental Bane
Grasping Vine
Greater Invisibility
Staggering Smite
Storm Sphere
Animate Objects
Antilife Shell
Circle of Power
Control Winds
Far Step

Armor: Light Armor and Shields
Weapons: Simple and Martial Weapons
Saving Throws: Intelligence and Constitution
Skills: Choose 3 from perception, arcana, nature, medicine, history, animal handling, and acrobatics.
Tools: Leatherworker’s Tools, Dragonchess

Starting Equipment:
a) A greatsword and leather armor.
b) A longsword, leather armor, 6 javelins, and a shield.
c) A longbow, a rapier, leather armor, a quiver with 30 arrows, and a shield.

a) An explorer’s pack and a leatherworker’s kit.

Hit Dice: D8
Hit Points at 1st level: 8 + your Constitution modifier
Hit Points at higher levels: 1d8 or 5 + your Constitution modifier for each level after 1st.

Dragon: When you take you first level in this class, you gain a pseudodragon companion with a permanent telepathic bond to you. You always know the location of your dragon as long as it is in the same plane as you. You and this dragon can read and speak draconic, and you can communicate with each other at a distance of a number of miles equal to your level. As an action, you can see through your dragon’s eyes. If your dragon is killed, you suffer one level of exhaustion from the stress of having your telepathic bond severed. You can spend a long rest to bring it back to life. If you do this, you end your long rest with 0 mana points.

Spellcasting: Unlike other spellcasters, your magic comes from the power your dragon bestowed on you when you met it; thus you have no spell slots. Instead, you have a maximum amount of mana equal to your Rider level. Intelligence is your spellcasting modifier for Rider spells. You regain all of your mana on a long rest. Whenever you cast a spell, you can spend 1 additional mana to cast it as if you were in your dragon’s location. You know 4 Rider spells from the Rider spell list and learn 1 more whenever you gain a level in this class. When you cast a Rider spell, you spend mana according to the table below. If you do not have enough mana, you cannot cast the spell.
Mana Cost:
1st Level- 1 Mana
2nd Level- 3 Mana
3rd Level- 5 Mana
4th Level- 7 Mana
5th Level- 9 Mana

Fighting Style: At level 2, choose between the Two Weapon fighting, Archery, Defense, Great Weapon Fighting, Dueling or Mariner fighting styles. You can’t benefit from the same fighting style more than once.

Mastery: At level 3, choose between the Spell Master and Weapon Master subclasses.

ASI: At levels 4, 8, 12, 16, and 19, you can increase 1 ability score by 2 or 2 ability scores by 1, or take a feat.

Draconic Growth: At level 5, your pseudodragon grows up into a wyrmling of your choice, but not a red one. No one can ride your wyrmling. Your wyrmling can only use its breath weapon once per short rest, unless it has multiple breath weapons, in which case it can only use each option once per long rest.

Improved Bond: At level 6, once per short rest, whenever you take damage, you can use your reaction to have your dragon take the damage instead. Additionally, once per short rest, your dragon can use its reaction whenever it takes damage for you to take the damage instead. Transferred damage cannot be reduced in any way. Additionally, you automatically succeed on any saving throw against your dragon’s breath weapon.

Draconic Tendencies: At level 9, your bonding with your dragon begins to influence you. You gain proficiency in survival and nature, your eyes continuously glow the color of your dragon, and you learn the Thaumaturgy cantrip.

Draconic Growth: At level 10, your dragon grows into a Young Dragon the same color as it was as a Wyrmling. One medium or two small creatures can ride on your dragon, but it has the same breath weapon limitations as before.

Extra Attack: At level 11, when you take the attack action, you can make two attacks instead of one.

Riding Master: At level 13, you have advantage on saving throws to stay on your dragon while it is in flight.

Greater Bond: At level 15, When a creature takes damage from your Dragon’s breath weapon, that creature has disadvantage on saving throws against your Rider spells until the end of your next turn.

Increased Draconic Tendacies: At level 17, you stop aging and can’t be aged magically. You are immune to disease.

Draconic Growth: At level 20, your dragon grows into an adult dragon of its color, 3 medium or 6 small creatures can ride it, and it is no longer is limited in uses of its breath weapon.

Weapon Master:
At level 3, when your dragon makes a critical hit on a creature, you have advantage on attacks against that creatures until the end of your next turn.

At level 7, when you cast a spell as an action, you can make one weapon attack as a bonus action.

At level 18, your ranged attacks have advantage while you are riding your Dragon, and if you move towards a creature at least 60 feet in a round, you first attack against that creature until the end of your next turn does an extra 4d10 piercing damage.

Spell Master:
At level 3, you regain mana points equal to your proficiency bonus whenever you complete a short rest.

At level 7, you can spend mana points as a bonus action to give yourself or your dragon hitpoints equal to the 5 times the mana points you spend.

At level 18, you learn one 6th and one 7th level spell from the sorcerer spell list, and can cast each once per long rest.